(1) Field of the Invention
The present invention relates to a multi-layer drawn polyester bottle and a process for the preparation thereof. More particularly, the present invention relates to a bottle having a wall biaxially molecularly oriented by drawing and an improved gas barrier property, which comprises a gas barrier layer of an ethylene-vinyl alcohol copolymer and a base layer of a polyester, and a process for the preparation of this bottle.
(2) Description of the Prior Art
At the present, formation of drawn polyester bottles is very popular, and since drawn polyester bottles have an excellent transparency and an appropriate gas barrier property, they are widely used as vessels for liquid products such as liquid detergents, shampoos, cosmetics, soys and sauces and also for carbonated drinks such as beer, cola and cider and refreshing drinks such as fruit juice and mineral water.
However, since a drawn polyester bottle is a kind of a plastic bottle, the drawn polyester bottle has a permeability to oxygen or carbon dioxide gas, though the permeability is very low, while the gas permeability of a completely sealed vessel such as a glass bottle or a metal can is substantially zero. Therefore, the drawn polyester bottle is inferior to a can or glass bottle in the preservability of a filled food, and when the drawn polyester bottle is used for a carbon dioxide gas-incorporated drink, loss of carbon dioxide gas is caused and in case of beer, cola or cider, the shelf life is apparently limited.
As means for improving the gas barrier property of a drawn polyester bottle, there has been proposed a method in which a drawn polyester bottle is coated with a polyvinylidene chloride resin, and a coated bottle of this type has been put into practical use. In order to improve a drawn polyester bottle having inherently an appropriate gas barrier property, it is of no significance to laminate or coat the drawn polyester bottle with a gas barrier resin which is inferior to the polyester in the gas barrier property. Namely, a resin having a higher gas barrier property than that of the polyester should be used for lamination or coating. Therefore, use of thermoplastic resins such as a vinylidene chloride resin, an acrylonitrile resin or a vinyl alcohol resin is expected, but an appropriate resin should be selected while taking the properties and processability of the resin into consideration.